Intake System Assessment for Central Columbia River

Four intake systems (vertical traveling screens, infiltration beds, perforated pipes located above the stream bed in the river channel, and perforated pipes located above the bed in an off-stream channel) are selected and considered for detailed evaluation of potential environmental impact. Based on all considerations of potential impacts, the best alternative is perforated pipes located above the river channel bed. This intake system is also the most economical to construct, operate, and maintain. A pivotal issue in assessing the environmental impact is the potential for impingement and entrainment of macroscopic planktonic organisms and juvenile fish without or with little swimming ability. As this impact depends largely upon approach velocities, the infiltration beds and perforated pipes located above the river channel bed are both well suited to minimize impingement and entrainment.